Move enable extensions define to a build flag.

chrome/browser/prefs/browser_prefs.cc

Index: chrome/browser/prefs/browser_prefs.cc
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 6af2627a29609b8e93fd27625a5dadc7e1b2d581..5ab02098809088caea49aa6947de04a22251561c 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -106,6 +106,7 @@
 #include "components/variations/service/variations_service.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_process_host.h"
+#include "extensions/features/features.h"
 #include "net/http/http_server_properties_manager.h"
 #include "printing/features/features.h"
 
@@ -118,7 +119,7 @@
 #include "chrome/browser/background/background_mode_manager.h"
 #endif
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
 #include "chrome/browser/accessibility/animation_policy_prefs.h"
 #include "chrome/browser/apps/shortcut_manager.h"
 #include "chrome/browser/extensions/activity_log/activity_log.h"
@@ -132,7 +133,7 @@
 #include "chrome/browser/ui/webui/extensions/extension_settings_handler.h"
 #include "extensions/browser/api/runtime/runtime_api.h"
 #include "extensions/browser/extension_prefs.h"
-#endif  // defined(ENABLE_EXTENSIONS)
+#endif  // BUILDFLAG(ENABLE_EXTENSIONS)
 
 #if BUILDFLAG(ENABLE_PLUGIN_INSTALLATION)
 #include "chrome/browser/plugins/plugins_resource_service.h"
@@ -371,7 +372,7 @@ void RegisterLocalState(PrefRegistrySimple* registry) {
   policy::BrowserPolicyConnector::RegisterPrefs(registry);
   policy::PolicyStatisticsCollector::RegisterPrefs(registry);
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   EasyUnlockService::RegisterPrefs(registry);
 #endif
 
@@ -513,7 +514,7 @@ void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {
   policy::URLBlacklistManager::RegisterProfilePrefs(registry);
   certificate_transparency::CTPolicyManager::RegisterPrefs(registry);
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   EasyUnlockService::RegisterProfilePrefs(registry);
   ExtensionWebUI::RegisterProfilePrefs(registry);
   RegisterAnimationPolicyPrefs(registry);
@@ -523,13 +524,13 @@ void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {
   extensions::ExtensionPrefs::RegisterProfilePrefs(registry);
   extensions::launch_util::RegisterProfilePrefs(registry);
   extensions::RuntimeAPI::RegisterPrefs(registry);
-#endif  // defined(ENABLE_EXTENSIONS)
+#endif  // BUILDFLAG(ENABLE_EXTENSIONS)
 
 #if defined(ENABLE_NOTIFICATIONS)
   NotifierStateTracker::RegisterProfilePrefs(registry);
 #endif
 
-#if defined(ENABLE_NOTIFICATIONS) && defined(ENABLE_EXTENSIONS) && \
+#if defined(ENABLE_NOTIFICATIONS) && BUILDFLAG(ENABLE_EXTENSIONS) && \
     !defined(OS_ANDROID)
   // The extension welcome notification requires a build that enables extensions
   // and notifications, and uses the UI message center.